Update git submodules

Update git submodules

* Update docs/submodules/appc.git from branch 'master'
  to 9c6141af9c6efbac352d6b4a63b3a60624d7ae9b
  - Improve security release notes

    In order to provide users with more details of project's state in
    terms of security let's divide the security release notes into three
    sections:

    - Fixed Security Issues
      Contains a list of security fixes merged during this
      release (especially those reported via OJSI tickets).

    - Known Security Issues
      Contains a list of vulnerabilities detected in project during
      release which have not been fixed yet and thus should be mitigated
      by the user.

    - Known Vulnerabilities in Used Modules
      Contains information about NexusIQ scan results

    Issue-ID: SECCOM-238
    Signed-off-by: Krzysztof Opasiak <k.opasiak@samsung.com>
    Change-Id: I9fee2338091ed5a879e0989d13501008d7d6013f